This invention relates to a displacement measuring method and displacement measuring apparatus capable of measuring displacements such as vibrations in a structure by installing a GPS receiver in the structure and detecting the position of that structure.
The real-time kinematic positioning method (RTK method) is a conventional method for measuring vibration components with centimeter-order precision, while maintaining real-time characteristics, using a GPS (global positioning system).
This method determines three-dimensional coordinates of a measurement target location by determining a carrier phase at the target location while referencing measured values of carrier phases from a GPS at a reference point for which the longitude, latitude, and altitude are known beforehand, and measures vibration components using time changes in the determined coordinate values.
However, when the distance between a satellite and a receiver at the measurement target location is being found by the carrier phase, it is necessary to determine integer bias ambiguity, and, in order to find the integer bias ambiguity, voluminous computations need be executed, which constitutes a problem.
An object of the present invention is to provide a GPS-based object displacement measuring method and displacement measuring apparatus which do not require integer bias ambiguity computations.
In order to attain the object stated above, the GPS-based object displacement measuring method according to the present invention is a method in which displacements of an object are measured by measuring carrier phases of radio waves emitted from at least three GPS satellites with a reference receiver deployed at a prescribed location and a measurement receiver deployed at the object, comprising the steps of:
dividing relative vectors indicating the relative positions of the two receivers into long period variation components not dependent on object displacements and short period variation components dependent on object displacements;
representing at least the short period variation components by x-, y-, and z-axis components for each unit vector directed toward the satellites from the reference receiver;
extracting short period phase components corresponding to the short period variation components of the relative vectors by measuring the carrier phases between the receivers and said at least three GPS satellites and passing these measured data through a band pass filter;
finding at least three receiver to receiver single differences between the receivers and the GPS satellites; and
computing the axial components for the short period variation components of the relative vectors based on said at least three receiver to receiver single differences.
In order to attain the object noted above, moreover, the GPS-based object displacement measuring apparatus according to the present invention is an apparatus in which displacements of an object are measured by measuring the carrier phases of radio waves emitted from at least three GPS satellites with a reference receiver deployed at a prescribed location and a measurement receiver deployed at the object, comprising:
a satellite angle measurement unit for receiving radio waves transmitted from the GPS satellites and measuring the elevations and azimuths of the satellites;
a carrier phase measurement unit for measuring the phases of carrier waves from the satellites;
a short period phase component extraction unit for passing the carrier phases measured by the carrier phase measurement unit through a band pass filter and extracting short period phase components that are time variation components;
a single difference computation unit for finding receiver to receiver single differences of the short period phase components extracted by the short period phase component extraction unit; and
a short period variation component computation unit for inputting the elevations and azimuths from the satellite angle computation unit and the receiver to receiver single differences from the single difference computation unit, respectively, producing at least three equations, solving these equations, and computing short period variation components of relative vectors.
As based on the configuration of the displacement measuring method and displacement measuring apparatus described above, relative vectors between the reference receiver and the measurement receiver are divided into long period variation components not dependent on object displacements and short period variation components dependent on object displacements. Then attention is given only to the short period variation components directly related to the object displacement, and the axial components of the relative vectors are found by computation based on the receiver to receiver single differences of the short period phase components that are short period variation components (components that are not dependent on integer bias ambiguity or displacements in satellite orbit) of carrier phases between the two receivers and the GPS satellites, whereby object displacements can be measured without finding integer bias ambiguity.
In order further to attain the object stated above, another GPS-based object displacement measuring method according to the present invention is a method in which a displacement of an object is measured by measuring the carrier phases of radio waves emitted from at least three GPS satellites with a reference receiver deployed at a prescribed location and a measurement receiver deployed at the object; comprising the steps of:
dividing relative vectors indicating the relative positions of the two receivers into long period variation components not dependent on object displacements and short period variation components dependent on object displacements;
representing at least the short period variation components by x-, y-, and z-axis components for each unit vector directed toward the satellites from the reference receiver:
extracting short period phase components corresponding to the short period variation components of the relative vectors by measuring the carrier phases between the receivers and the at least three GPS satellites and passing the measured data through a band pass filter;
finding at least three receiver to receiver/satellite to satellite double differences between the receivers and the GPS satellites; and
computing the axial components for the short period variation components of the relative vectors based on the at least three receiver to receiver/satellite to satellite double differences.
In order to further attain the object noted above, another GPS-based object displacement measuring apparatus according to the present invention is an apparatus in which a displacement of an object is measured by measuring the carrier phases of radio waves emitted from at least three GPS satellites with a reference receiver deployed at a prescribed location and a measurement receiver deployed at the object, comprising:
a satellite angle measurement unit for receiving radio waves transmitted from GPS satellites and measuring the elevations and azimuths of these satellites from data contained in the navigation messages thereof;
a carrier phase measurement unit for measuring the phases of carrier waves; a short period phase component extraction unit for passing the carrier phases measured by the carrier phase measurement unit through a band pass filter and extracting short period phase components that are time variation components;
a single difference computation unit for finding receiver to receiver single differences of the short period phase components extracted by the short period phase component extraction unit;
a double difference computation unit for finding receiver to receiver/satellite to satellite double differences of short period phase components that are satellite to satellite single differences of receiver to receiver single differences extracted by the single difference computation unit; and
a short period variation component computation unit for inputting elevations and azimuths from the satellite angle computation unit and the receiver to receiver/satellite to satellite double differences from the double difference computation unit, producing at least three equations, solving these equations, and computing short period variation components of relative vectors.
As based on the configuration of the displacement measuring method and displacement measuring apparatus described above, relative vectors between the reference receiver and the measurement receiver are divided into long period variation components not dependent on object displacements and short period variation components dependent on object displacements. Then attention is given only to the short period variation components directly related to the object displacement, and the axial components of the relative vectors are found by computation based on the receiver to receiver/satellite to satellite double differences of the short period phase components that are short period variation components (components that are not dependent on integer bias ambiguity or fluctuations in satellite orbit) of carrier phases between the two receivers and the GPS satellites, whereby object displacements can be measured without finding integer bias ambiguity.
Various features and benefits of the present invention will be apparent from embodiments which will be described with reference to the attached drawings.